A very strange thing is happening in Librecad 2.2.0.
I changed the units' precision from 0.0000 to 0.00; after this, I created a circle but, when I put a linear dimension in the drawing, the dimension is still in 0.0000 ...
I also tried to close and reopen the drawing, closed and started a new drawing, but the precision remains the same.
A small precision like 0.0 is all I need, but the software doesn't accept my command.
What shall I do to put the dimensions in the precision I need?
What you have changed in the Units tab is the precision of the coordinates in the bottom left corner.
Switch to the after next tab Dimensions, where you can change the dimensions precision.
Ref.: https://librecad.readthedocs.io/en/latest/ref/draw-prefs.html?highlight=dimensions#dimensions